I have a project which should be as power-saving as possible.
I program with Atmel Studio, and put all the Arduino runtime source files into my project folder and compile them with my program.
Now I'd like to know which F_CPU values are supported. I mean that every runtime function works as intended.
If only 16Mhz is supported, can you guide me which functions are clock-agnostic so I can create ifdefs for different F_CPU values there. I guess these are for example serial init functions.
Thank you for your help 
16, 8, 4, 2, 1 MHz. Assuming you are using an AVR processor.
I tried my project with 8Mhz internal clock source and it worked fine.
Then I set CKDIV8 for 1Mhz but it didn't work. I have a stepper motor which turns very slow.
Any idea?
Library you are using does not support 1 MHz?
I'm using FreeRTOS-AVR which is configured as:
#define configCPU_CLOCK_HZ ( ( unsigned long ) F_CPU )
#define configTICK_RATE_HZ ( ( TickType_t ) (F_CPU/16384L))
this should work IMHO
Kyromaster:
I'm using FreeRTOS-AVR
I'm not going down that rabbit hole. Someone else will have to help.